Souls will be server bound when you get them so you would have to purchase a new soul that you could use on the second server. That being said, you would not have to purchase a new copy of the game or make a different account to have a character on more than one server.
Sparks of life though are not server bound in any way as they simply let you put your soul into a character.
Also naturally all of your stuff from your character on one server will never be able to transfer over to another server as the game is a persistent world and you can't move stuff/characters between the servers.